Circuit interrupter



June 21, 1949. B. P. BAKER ET AL CIRCUIT INTERRUPTER Filed April 30, 1945 Insulation INVENTORS Benjamin P. Baker Roswell 6'. Van'SZ'c/cl and iames M Cumming. 1/ ATTORNE Patented June 21, 1949 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER Application April 30, 1945, Serial No. 591,046

4 Claims.

This invention relates to circuit interrupters, in general, and, more particularly, to circuit interrupters of the liquid-break type in which arc extinction is effected by a flow of an arc-extinguishing liquid.

In United States Patent 2,253,009, which issued August 19, 1941, to Benjamin P. Baker, and which is assigned to the assignee of the instant application, there is disclosed and claimed a novel circuit interrupting structure in which a piston member carrying a movable contact causes a separation of the latter from a relatively stationary contact to draw an arc. The piston member has a plurality of surface irregularities, and the piston member moves into a piston chamber, the inner walls of which also have a plurality of surface irregularities. The surface irregularities on both the piston member and on the inner Walls of the piston chamber serve to retain a plentiful supply 'of arc-extinguishing liquid, such as oil, adjacent to the established arc as it is drawn into the piston chamber adjacent the foregoing surface irregularities. The piston action caused by the piston member moving into the piston chambers sends a flow of liquid longitudinally of the arc to effect its extinction. The interrupting structure described in this patent is particularly effective for interrupting low currents inasmuch as the arc voltage is low, and also the arc energy is very low. Consequently, this interrupter is particularly adapted to porcelain-clad or oil-poor breaker designs.

However, in adapting the aforesaid interrupting structure for the interruption of larger currents at higher voltages, the accumulated gas tends to impose a retarding action on the opening movement of the piston member. It is an object of our invention to improve this interrupting structure and adapt it for the interruption of larger currents at higher voltages without the use of heavy accelerating springs to impose a heavy burden on the operating mechanism.

It is a further object of our invention to provide acceleration, in addition to that provided by the opening spring, by the use of an auxiliary series are for generating pressure acting on a piston which helps to move the interrupter to open position.

In United States Patent 2,452,477 which issued Oct. 26, 1948, to Winthrop M. Leeds, and which i is assigned to the assignee of the instant appli cation, there is disclosed and claimed a modification of the foregoing Baker interrupting structure in which a serially related pressuregenerating arc is utilized to speed up the moving parts of the interrupting structure during the interruption of high currents. It is an object of our invention to provide further improvements in the interrupting structure of the aforesaid Leeds patent.

We have discovered that interruption of an arc is not possible until the arc has attained a predetermined length. Prior to the attainment of this predetermined length, the flow of oil sent toward the are merely results in contaminating the oil without producing any useful results. Consequently, it is a further object of our invention to improve the Baker interrupting structure in such a manner as to delay the flow of oil toward the interrupting are for a predetermined time following contact separation.

Another object is to provide an improved interrupting structure which will more effectively interrupt the circuit than has heretofore been obtained.

Another object is to provide a circuit interrupter in which improved differential piston means are incorporated to send fluid toward the are drawn therein.

Further objects will readily become apparent upon a reading of the following specification taken in conjunction with the drawing, in which:

Figure 1 is a cutaway view of a circuit inter: rupter embodying our invention and shown in the closed circuit position;

Fig. 2 is an enlarged vertical sectional view of the left-hand arc-extinguishing unit shown in Fig. 1, the parts being disposed in the closed circuit position;

Fig. 3 is a view similar to Fig. 2 but showing the disposition of the parts at an intermediate point in the opening operation just prior to the time at which oil flow is sent toward the arc;

Fig. 4 is a view similar to Fig. 3 but showing the disposition of the parts during the interruption of low currents;

Fig. 5 is a view similar to Fig. 4 but showing the disposition of the parts during the interruption of high currents;

Fig. 6 is a view in section taken along the broken sectional line VI-VI of Fig. 4; and

Fig. 7 is a view in section taken along the line VII-VII of Fig. 2.

Referring to the drawing and more particularly to Fig. 1 thereof, the reference numeral I designates a tank in which a suitable arc-extinguishing fluid 2, such as oil, is filled to the level 3. Depending from the cover 4 of the tank I are two insulating bushings 5, 6 through which extend terminal studs, not shown. At the lower end of the terminal studs are threadedly secured contact feet I, 8.

The contact feet I, 8 serve to support in position an identical pair of arc-extinguishing units 9 which are bridged in the closed circuit position of the interrupter, as shown by the full lines in Fig. 1, by a conducting bridging member II] reciprocally operated during the opening and closing operations by an insulating operat ing rod II actuated by suitable operating mechanism, not shown. 7

Referring to Fig. 2, which shows in vertical section the left-hand arc-extinguishing unit 9 of Fig. 1, with the contact foot T omitted for purposes of clarity, it will be apparent that a conductng plate I2 is provided havinga depending portion I3 to which is suitably secured a stationary contact I4. The plate I2 is secured by suitable means, not shown to a metallic ring shaped member I5 which is threadedly secured I6 to the upper end'of the insulating casing I7. Positioned on a shoulder I'8for'm'ed on the inner wall of the casing I1 is aninsula'ting stop member I 9 having formed therein a plurality of apertures ZII. Immediately above the stop member I9 are disposed in stacked relation a plurality of washer members 2| of insulating material which form acylindrical passage or a first piston chamber 22. At the side of the cylindrical passage 22 adjacent to the point at which the interrupt ng are 23' is established, the washer members 2I are alternately notched toform' a' plurality or surface irregularities along the length of the cylindrical passage 22.

A sleeve 24 positioned between the top washer member 2'I andthe ring-shaped member 5' serves tohol'd the washer'niembers 2i and the stop member I9 fixedly in position. Movable within the cylindrical passage or piston chamber 22 is a first piston member, generally designated by the reference numerai 25. The" first piston member 25 carries a first movabl'e'cont'act 26 which engages in the closed circuit position of the interrupter with the stationary contact I4, as shown in Fig 2. suppo ted on and above the first movable contact 26 by two insulating rods 2! are a plurality of insulating plates 28. The insulating plates 28 are notched in such an alternate manner, as shown in Fig. 6 to provide a longitudinal corru gated portion 29 which is drawn adjacent to the interrupting are 23' during the openin operation.

Forming a portion of the piston member 25 and threadedly'secured to the upper portion thereof at 30 is a suitably shaped insulatingsecond piston member 3| slidably guided by the lower inner wall of the casing H. An accelerating compression spring 32 is positioned between the member 3 I' and thestop'm'ember I9;

Associated with the second piston member 31" are valve means, generally designated-by the refer"- ence" numeral- 33} The lower portion of the piston member is made of conducting material and forms a second movable contact 34 which co-operates in the closed circuit position of the interrupter, as shown in Fig. 2, with a third movable contact 35 assuming the shape of a conducting rod. Integr'ally formed with the third movablecontact 35 is a flange 36, which serves during. the closing operation to pick up the insulating valve 31 forming part of the'valve means 33, Slidably' surrounding a portion 38 of the first piston member 25 is a sleeve 39 which closely moves within the cylindrical passage 22, the purpose for which will appear more clearly hereinafter.

The operation of the arc-extinguishing unit 9 will now be explained. In the closed circuit posh tion of the interrupter, as shown by the full lines in 1 and also in Fig. 2, the electrical circuit therethrough comprises terminal stud, not shown, contact foot I, conducting plate I2, depending portion I3, stationary contact I4, first movable contact 25, through conducting portion 38, second movable contact 34, third movable contact 35, through the conducting bridging member l5 and through the right-hand arc-extinguishing unit 9 in an identical manner to the right-hand terminal stud, not shown. When it is desired to open the electrical circuit passing through the interrupter, or in response to overload conditions existing in the electrical circut controlled by the interrupter, suitable operating mechanism, not shown, is actuated to cause a downward movement of the insulating operating rod I I. The downward movement of the operating rod II also causes downward movement of both third movable contacts 35 disposed at the extremities of the conducting bridging member ID.

Considering only the operation'of the'left-hand arc-extinguishing unit 9, andassumingthe'interruption of relatively low current, it will be apparent, referring to Figs. 3 and 4, that the downward movement of the'third movable contact 35 permits the accelerating compression" spring 32 to force the secondpistonmember 3 I downwardly. Thedownward movement of'themember 3 I'serves to also drive downwardly the first piston member 25 separating the first movable contact 26 from the stationary contact I4 to establish an interrupting are 23 axially along the inner wall of the piston chamber 22, as shown in Figs. 3' and 4. It will be apparent that the insulating plates 2! form a piston chamber, generally designated by the reference numeral 22, into which the piston member 25 is driven during'the opening operation. Also, it will be apparent that the plates 28 form a following member, generally designated by the reference numeral 4| which follows the first movable contact 26 into the piston chamber 22'.

For a predetermined time following the separation of the contacts I4, 26, the sleeve 39 moves with the first piston member 25 to thereby cause no oil flow adjacent the interrupting are 23. However, when th sleeve 39 strikes the portion 42 of the stop member I9, the downward motion of the sleeve 39 willbe halted and thereafter the continueddownward movement of the piston member 25 will cause a longitudinal flow 01 oil upwardly adjacent the interrupting are 23. During the interruption of low currents, the third movable contact member 35 separates from the second movable contact 34 to draw an arc 45 as shown in Fig; 4 generating. little pressure. The downward movement of the second piston member 3| will serve to draw oil through. the opening 43 associatedwitli the valve means- 33 and into the substantially enclosed second piston chamber 44 below the stop member I9.- During'no-load interruption, that is, opening the breaker v/ith no current passing therethrough, the same action takes place, that is, oilbeingdrawn-throug-h the opening 43, the valve means 33 being open.

During the interruption of relatively high currents, there will be a deceleration in the downward speed of the first piston member 25' when the sleeve 39 strikes the portion: 42 of the stop member I9. At this time, the thirdmovable contact 35 will separate from the second movable contact 34 to establish a pressure-generating are 45, as shown in Fig. 5. The pressure generated at the pressure-generating are 45 will act along the contact to close the valve means 33, thereby closing the openings 43. The pressure in the region 44 drives the second piston member downwardly, thus assisting the accelerating compression spring 32 in causing an opening operation of the interrupter. It will be observed that if the third movable contact 35 separates a considerable distance from the second movable contact 34, the pressure-generating are will be lengthened to increase the gas generation at this are. The increased gas generation will cause an increased pressure to take place within the region 44 and to accelerate the downward movement of the second piston member 3| and, consequently, the downward movement of the first piston member 25. The increased downward movement of the piston member 25 will cause the piston mem ber 25 to tend to catch up with the third movable contact 35, thereby shortening the pressuregenerating arc 45. As a result, excessive pressure within the region 44 will cause the gap between the contacts 34, 35 to be shortened, and thus the arc length of the pressure-generating are s5 tends to be adjusted automatically so as to keep the speed of the moving contact 34 very close to that of the movable contact 35.

The longitudinal flow caused by the piston action of the piston member 25 moving into the piston chamber 22 will pass upwardly adjacent the are 23 to pass out of the unit 9 through the vents 41 provided through the conducting plate it. The contact foot I has suitable apertures provided therein, as shown in Fig. 1, to permit a free venting of fluid, out of the vents 41 and to the region exterior of the arc-extinguishing unit 5.

In the full open circuit position of the interrupter, the third movable contact 35 is completely withdrawn from the arc-extinguishing unit 9 to introduce an isolating gap in the circuit. Thus, in the full open circuit position, fresh oil may enter the region 44 through the opening 48 which is provided following withdrawal of the third movable contact 35 from the unit 3. Also, fresh oil may enter the upper end of the unit 3 through the vents 41.

During the closing operation of the interrupter, the third movable contact 35 moves upwardly, entering the opening 48 through valve 37!, the flange 36 picking up the valve 3'! to open the vents 43. The movable contact 35 strikes the second movable contact 34 to thereby cause raising of the piston member 25, thus charging the accelerating compression spring 32 until re-engagement is eifected between the contacts I4, 26, thus closing the electrical circuit through the interrupter.

It will be observed that during the closing operation when the contacts I4, 26 approach each other, an arc may be formed therebetween when the interrupter is employed on a high voltage circuit. Whatever pressure is developed by such a closing arc between the contacts 4, 26 will then have no appreciable elfect either to accelerate or to stall the motion of the piston member 25 since there are no unbalanced piston surfaces acted upon by the pressure created at this closing arc, the chamber 5!] being freely vented by the vents 41.

It will be observed that during the opening operation that the delay of the starting of the oil flow adjacent the interrupting are 23 causes the moving parts of the interrupter to get up to speed, thereby intensifying the oil flow once the sleeve 39 has struck the portion 42 of the stop member l9. Also, it will be observed that the longitudinal corrugated portion 29 associated with the following member 4| co-operates with the corrugated portion of the piston chamber 22, caused by the plates 2| being alternately notched, to retain a plentiful supply of oil adjacent the interrupting are 23 and to increase the turbulence thereat during the opening operation to facilitate the extinction thereof.

From the foregoing description it will be apparent that we have provided a novel structural arrangement whereby an interrupter of the type described in the aforesaid Baker patent may be adapted for the interruption of large amperage currents at high voltages. Also, we have disclosed the advantage of delaying for a predetermined time following contact separation the flow of oil adjacent the interrupting" arc. A predetermined arc length is necessary for interruption. This delay provided in our invention permits the moving parts of the breaker to get rapidly up to speed, thereby drawing very rapidly the predetermined arc length necessary for interrupt-i011. Also another advantage is that the delay in oil flow minimizes contamination of the oil during the time when interruption is not possible anyway prior to the attainment of this predetermined arc length. An interrupter used in oil-poor breaker construction should contaminate the oil little as possible, inasmuch as such contamination necessitates a more frequent renewal of the oil within the breaker.

By the above construction we have speeded up the moving parts of the breaker during highcurrent interruption without employing additional accelerating compression springs to increase the closing load imposed on the operating mechanism.

Although we have shown and described a specific construction, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. A circuit interrupter of the liquid break type including means defining a substantially cylin drical piston chamber, means venting one end of the piston chamber, a relatively stationary contact disposed adjacent one side wall of the piston chamber and also adjacent the vented end thereof, a generally cylindrical movable piston member movable within the piston chamber and carrying a movable contact at one side thereof, an insulating follower member carried by the piston member and restricting the are drawn into the piston chamber longitudinally thereof along the inner wall thereof, a movable sleeve member surrounding the movable piston member, stationary stopping means to limit the opening motion of the sleeve member into the piston chamber, means movable with the piston member for picking up the sleeve member during the closing stroke to move the latter away from its stopping means, the sleeve moving with the piston member during the initial lengthening of the arc to prevent liquid flow out of the piston chamber until the sleeve strikes the stopping means at which time only liquid is forced longitudinally of the lengthening arc out of the piston chamber.

2. A circuit interrupter of the liquid break type including means defining a piston chamber, means venting the piston chamber at one end thereof, a stationary contact disposed adjacent the vented end of the piston chamber adjacent one side wall thereof, a movable piston member movable within the piston chamber and carrying a movable contact along one side wall thereof, a follower member carried by the piston member to restrict the arc established between the two contacts and drawn into the piston chamber along the inner wall thereof, means initially movable with the piston member into the piston chamber to delay the flow of liquid longitudinally of the established arc, stopping means for the last-mentioned means to stop the opening motion thereof to only at this time permit forcing of liquid out of the piston chamber by the pumping action of the piston member.

3. A circuit interrupter of the liquid break type including means defining a piston chamber, means venting the piston chamber at one end thereof, a stationary contact disposed adjacent the vented end of the piston chamber adjacent one side wall thereof, a movable piston member movable within the piston chamber and carrying a movable contact along one side wall thereof, a

follower member carried by the piston member to 4 restrict the are established between the two contacts and drawn into the. piston chamber along the inner wall thereof, means initially movable with the piston member into the piston chamber to delay the flow of liquid longitudinally of the established arc, stopping means for the lastmentioned means to stop the opening motion thereof to only at this time permit forcing of liquid out of the piston chamber by the pumping action of the piston member, means establishing a second serially related pressure-generating arc, and means utilizing the pressure established at the second serially related pressure-generating arc to facilitate opening motion of the movable piston member.

4.. A circuit interrupter of the liquid break type including means defining a substantially cylindrical piston chamber, means: venting one end of the piston chamber, a relatively stationary contact disposed adjacent one side wall of the piston chamber and also adjacent the vented end thereof, a generally cylindrical movable piston member movable within the piston chamber and carrying a movable contact at one side thereof, an insulating follower member carried by the piston member and restricting the are drawn into the piston chamber longitudinally thereof along the inner wall thereof, a movable sleeve member surrounding the movable piston member, stationary stopping means to limit the opening motion of the sleeve member into the piston chamber, means movable with the piston member for picking up the sleeve member during the closing stroke to move the latter away from its stopping means, the sleeve moving with the piston member during the initial lengthening of the arc to prevent liquid flow out of the piston chamber until the sleeve strikes the stopping means at which time only liquid is forced longitudinally of the lengthening are out of the piston chamber, means establishing a second serially related pressure-generating arc, and means utilizing the pressure established at. the second serially related pressure-generating arc to facilitate opening motion of the movable piston. member.

BENJAMIN P. BAKER.

ROSWELL C. VAN SICKLE.

JAMES M. CUMMING.

REFERENCES CITED The following references are of record in the this patent:

UNITED STATES PATENTS Number Name Date Re. 18,257 Paul Nov. 24, 1931 2,196,419 Leeds et al Apr. 9, 1940 2,372,589 Leeds et a1 Mar. 27, 1945 2,406,469 Ludwig et al Aug. 27, 1946 

